1. Field of the Invention
This invention relates to a telephoto lens for a camera, and particularly to an internal focusing telephoto lens suitable for use in an auto focus camera such as a single-lens reflex camera or an electronic still camera.
2. Related Background Art
An internal focusing telephoto objective lens which comprises three positive, negative and positive lens units and in which the middle negative lens units is moved in the direction of the optical axis to accomplish focusing is known. Heretofore, however, in the internal focusing telephoto objective lens of this type, the movement distance of the focusing lens unit has been very long when focusing is effected. That is, when the focal length is lengthened to increase the photographing magnification, it has led to the tendency that the movement distance of the focusing lens unit also becomes long. This is turn has led to the disadvantage that the burden of a motor for auto focus driving becomes great and a lens moving mechanism for focusing becomes bulky.